A page fault happens when a running programme references a memory address that the CPU cannot find in physical RAM. The operating system intercepts this request and must locate the required data on the hard drive or SSD, load it into memory, and resume the programme. This is a fundamental part of virtual memory management.
Modern operating systems use virtual memory to give each programme the illusion of having access to far more memory than physically exists. The system divides memory into fixed-size blocks called pages. When a programme needs data that isn't in RAM, the CPU triggers a page fault exception. The operating system then retrieves the required page from storage and swaps it into physical memory, possibly removing another page to make space.
Why this matters. Page faults are normal and necessary for modern computing. However, excessive faults slow performance significantly because disk access is thousands of times slower than RAM access. When a system constantly pages data in and out, performance degrades noticeably. This condition is called thrashing.
Common scenarios. Opening large files, running many programmes simultaneously, or working with datasets larger than available RAM all trigger page faults. Gaming performance drops when your PC lacks sufficient RAM because textures and assets must load from disk repeatedly. Video editing software with limited memory also causes frequent faulting.
What you can do. If your system feels sluggish and you see high disk activity during routine tasks, you likely have too many page faults. Adding more RAM is the most effective solution. You can also monitor page fault rates using Windows Task Manager or macOS Activity Monitor to diagnose memory pressure. Close unnecessary programmes and limit browser tabs to reduce demand on available memory.